Recent years have seen rapid reductions in the size and weight of electronic devices such as mobile telephones, video cameras, and laptop personal computers. This development essentially requires flexible printed circuit boards, which are soft printed circuit boards with flexibility. Further, an increasing number of electronic circuits have narrower pitches and operate on higher frequencies, which has increased the importance of dealing with electromagnetic wave noises generated as a result of the narrower pitches and higher frequencies. In view of this, there has been a technique of including in a flexible printed circuit board an electromagnetic wave shielding member for shielding or absorbing an electromagnetic wave noise generated by an electronic circuit. A known flexible printed circuit board having the electromagnetic wave shielding function is a flexible printed circuit board including (i) an insulating layer provided with a shielding layer that is bonded thereto and that includes layers such as a conductive adhesive layer and a thin metal film layer and (ii) a ground line to which the thin metal film layer is electrically connected (see, for example, Patent Literature 1).
A flexible printed circuit board is also provided with an insulator film serving as a surface protecting material. Regarding such an insulator film, there has been a technique of giving the black color to an insulator film to impart concealment property to the insulator film, thereby concealing the circuit pattern to protect confidential information included in the circuit pattern (see, for example, Patent Literatures 2 and 3).